Moreover it is well known and easy to show that
αn = αFn + Fn−1 (1.6)
and
βn = βFn + Fn−1
for every n ∈ Z. On the other hand, it can be shown by induction that
F 2
n − FnFn−1 − F 2
n−1 = (−1)n+1 (1.7)
for every n ∈ Z. Now we give a theorem from [4], which is related to the set of the units of the ring Z[α] where
Z[α] = {aα + b : a, b ∈ Z}.